Cleanliness study of SWRH82B hard wire steel produced by BOF-LF-CC processes

The cleanliness evolution of SWRH82B steel produced by the BOFLFCC process was studied by systematic sampling and lab comprehensive analysis. The results show that the content of oxygen and the number of micro-inclusions significantly decrease after calcium treatment,while the content of nitrogen in molten steel slightly increases. Both the contents of oxygen and nitrogen sharply increase during the casting process. 97% of the micro-inclusions in casting billets are smaller than 5 μm. They mainly include trenchant angularity single Al₂O₃ inclusions,spherical complex inclusions of oxides with Ca S and Mn S,and complex inclusions of simple oxides or nitrides with Mn S. Calcium treatment after LF refining removes oxygen from molten steel efficiently,but increase the amount of Al₂O₃ inclusions in casting billets,which is harmful to the quality of SWRH82B steel. Due to serious lag entrapment,refractory erosion and reoxidation caused by unreasonable tundish structure,the cleanliness of liquid steel decreases.